Early Pseudomonas aeruginosa infection in individuals with cystic fibrosis: Is susceptibility testing justified?

D. Macdonald, L. Cuthbertson, C. Doherty, S. Campana, N. Ravenni, G. Taccetti, J. R W Govan

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    Objectives: To test the presumption that Pseudomonas aeruginosa isolates responsible for initial lung infection in individuals with cystic fibrosis (CF) are invariably susceptible to antipseudomonal agents. Methods: Antibiotic susceptibility was determined (MIC and Etest) in two populations of P. aeruginosa associated with initial lung infection. Population 1: environmental isolates (n=78). Population 2: clinical isolates responsible for first infection in previously non-infected patients (85 isolates from 85 patients). Susceptibility or resistance was determined using current BSAC guidelines; ninth version (2009). Results: The majority (≥90%) of isolates in both bacterial populations were susceptible to the front-line antipseudomonal agents; colistin, ciprofloxacin, tobramycin, ceftazidime, amikacin and meropenem. Up to 10% of isolates were resistant to one or more antibiotics. A single isolate from each population would be defined as resistant to tobramycin based on a breakpoint (>128 mg/L) that has been suggested for use in patients receiving inhaled therapy. Conclusions: The high prevalence of susceptibility found in P. aeruginosa isolates associated with initial infection contrasts with the high prevalence of resistance found in isolates from chronic CF lung infection. However, susceptibility in early isolates cannot be presumed. Until further data are obtained from clinically based studies, susceptibility tests should continue to be performed to assist the choice of antibiotics for treatment of early infection. © The Author 2010. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved.
    Original languageEnglish
    Article numberdkq342
    Pages (from-to)2373-2375
    Number of pages2
    JournalJournal of Antimicrobial Chemotherapy
    Issue number11
    Publication statusPublished - 13 Sept 2010


    • Antibiotics
    • Environmental
    • Etest
    • Resistance


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